diff options
| author | Jiri Pirko <jiri@mellanox.com> | 2017-08-22 22:46:49 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-08-22 14:39:58 -0700 |
| commit | 744a4cf63e528c29840f45811d6fb93fd129b87d (patch) | |
| tree | e30c1aaf57d0f0bcdab8b26bc49badb2d8b673b2 | |
| parent | fd6055a806edc4019be1b9fb7d25262599bca5b1 (diff) | |
net: sched: fix use after free when tcf_chain_destroy is called multiple times
The goto_chain termination action takes a reference of a chain. In that
case, there is an issue when block_put is called tcf_chain_destroy
directly. The follo-up call of tcf_chain_put by goto_chain action free
works with memory that is already freed. This was caught by kasan:
[ 220.337908] BUG: KASAN: use-after-free in tcf_chain_put+0x1b/0x50
[ 220.344103] Read of size 4 at addr ffff88036d1f2cec by task systemd-journal/261
[ 220.353047] CPU: 0 PID: 261 Comm: systemd-journal Not tainted 4.13.0-rc5jiri+ #54
[ 220.360661] Hardware name: Mellanox Technologies Ltd. Mellanox switch/Mellanox x86 mezzanine board, BIOS 4.6.5 08/02/2016
[ 220.371784] Call Trace:
[ 220.374290] <IRQ>
[ 220.376355] dump_stack+0xd5/0x150
[ 220.391485] print_address_description+0x86/0x410
[ 220.396308] kasan_report+0x181/0x4c0
[ 220.415211] tcf_chain_put+0x1b/0x50
[ 220.418949] free_tcf+0x95/0xc0
So allow tcf_chain_destroy to be called multiple times, free only in
case the reference count drops to 0.
Fixes: 5bc1701881e3 ("net: sched: introduce multichain support for filters")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/sched/cls_api.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index 9fd44c221347..45cd34eee727 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -215,9 +215,17 @@ static void tcf_chain_flush(struct tcf_chain *chain) static void tcf_chain_destroy(struct tcf_chain *chain) { - list_del(&chain->list); + /* May be already removed from the list by the previous call. */ + if (!list_empty(&chain->list)) + list_del_init(&chain->list); + tcf_chain_flush(chain); - kfree(chain); + + /* There might still be a reference held when we got here from + * tcf_block_put. Wait for the user to drop reference before free. + */ + if (!chain->refcnt) + kfree(chain); } struct tcf_chain *tcf_chain_get(struct tcf_block *block, u32 chain_index, |